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Special Session 1: Ecosystem under multiple stressors |
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High and dry: which species are most vulnerable to heat stress on tropical shores?
Wednesday 11th @ 1212-1229
Multi-function Hall
Gray A. Williams* , The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong
Jasmine Ng, The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong
Monthon Ganmanee, Department of Animal Production Technology and Fisheries, King Mongkut's Institute of Technology Ladkrabang, Bangkok, Thailand
Yun-Wei Dong, State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University
Guo-Dong Han, State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University
Terence PT Ng, The Swire Institute of Marine Science and School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong
Presenter Email: hrsbwga@hku.hk
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| Tropical species are assumed to be living close to the edge of their physiological limits, and therefore especially vulnerable to extreme climates. This is especially considered to be true for high shore species living on tropical rocky shores where heavy mortality is often recorded due to high temperatures, especially during summer months. On semi-exposed shores in Hong Kong a variety of molluscan grazers including littorinids; true and false limpets; topshells; nerites and chitons dominate the shore. Each year, these grazers exhibit high mortalities, yet patterns do not simply match the physiological tolerances of the different taxa but are also related to behavioural responses to thermal stress. Integrating a variety of different metrics of ‘thermal stress’ reveals that the coiled gastropods are the most resistant, as they can isolate themselves from environmental extremes. Limpets and chitons, as a result of their body plans are, physiologically the most vulnerable, as environmental conditions frequently exceed their thermal tolerances. Heavy mortality rates are observed in the limpets but not the most vulnerable group, the chitons, which escape heavy mortality on account of their behaviour and flexible morphology. The combination of physiological tolerance, which is linked to taxonomy, and behavioural responses plays an important role in determining how close to their thermal limits many mobile taxa are living on tropical shoes. This integrative response is contrasted by sessile species, such as the oyster Isognomon, which is unable to escape heat stress but instead has physiological responses to combat extreme heat. The combination of these different strategies determines the niches available to intertidal species, and it appears that in contrast to popular belief, high shore tropical species are not the most vulnerable species to thermal stress. |
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